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Questions and Answers
What is the primary function of microtubules in eukaryotic cells?
What is the primary function of microtubules in eukaryotic cells?
- Segregate chromosomes during cell division (correct)
- Make up the plasma membrane
- Aid in cell movement
- Anchor organelles
Eukaryotic cells do not possess membranous organelles.
Eukaryotic cells do not possess membranous organelles.
False (B)
What term describes the structure of the plasma membrane?
What term describes the structure of the plasma membrane?
fluid mosaic
The __________ regulates the exchange of materials with the environment.
The __________ regulates the exchange of materials with the environment.
Match the following cytoskeleton components with their characteristics:
Match the following cytoskeleton components with their characteristics:
What is the primary function of mitochondria?
What is the primary function of mitochondria?
Aerobic cellular respiration occurs only in the presence of carbon dioxide.
Aerobic cellular respiration occurs only in the presence of carbon dioxide.
What is the process of dividing the nucleus and its contents called?
What is the process of dividing the nucleus and its contents called?
DNA replication occurs during the _____ stage of interphase.
DNA replication occurs during the _____ stage of interphase.
Match the following phases of mitosis with their descriptions:
Match the following phases of mitosis with their descriptions:
Which enzyme is crucial for adding nucleotides during DNA replication?
Which enzyme is crucial for adding nucleotides during DNA replication?
Meiosis results in four identical gametes.
Meiosis results in four identical gametes.
What are telomeres and why are they important?
What are telomeres and why are they important?
Mitochondria are _____ inherited.
Mitochondria are _____ inherited.
Match the following terms with their definitions:
Match the following terms with their definitions:
What is the summary reaction formula for aerobic cellular respiration?
What is the summary reaction formula for aerobic cellular respiration?
Interphase consists of three stages: G1, G2, and M phase.
Interphase consists of three stages: G1, G2, and M phase.
How many chromosomes do gametes contain compared to somatic cells?
How many chromosomes do gametes contain compared to somatic cells?
Which of the following proteins change shape to move solutes across the membrane?
Which of the following proteins change shape to move solutes across the membrane?
Active transport requires metabolic energy, typically in the form of ATP.
Active transport requires metabolic energy, typically in the form of ATP.
What is the primary function of the sodium-potassium (Na+-K+) pump?
What is the primary function of the sodium-potassium (Na+-K+) pump?
The movement of substances out of cells is called exocytosis.
The movement of substances out of cells is called exocytosis.
Match the terms with their descriptions:
Match the terms with their descriptions:
What type of transport involves moving two solutes simultaneously?
What type of transport involves moving two solutes simultaneously?
Transcytosis involves the movement of substances into cells followed by their movement out of cells.
Transcytosis involves the movement of substances into cells followed by their movement out of cells.
Define osmosis.
Define osmosis.
When both solutes flow in the same direction during secondary active transport, this is called symporters_.
When both solutes flow in the same direction during secondary active transport, this is called symporters_.
Which statement is true regarding cyanide's effect on active transport?
Which statement is true regarding cyanide's effect on active transport?
What percentage of the membrane is made up of phospholipids?
What percentage of the membrane is made up of phospholipids?
Saturated fatty acids increase membrane fluidity.
Saturated fatty acids increase membrane fluidity.
Define membrane fluidity.
Define membrane fluidity.
Cholesterol serves as a _____ buffer for membrane fluidity.
Cholesterol serves as a _____ buffer for membrane fluidity.
Match the following membrane components with their functions:
Match the following membrane components with their functions:
Which type of molecules can travel through the membrane without assistance?
Which type of molecules can travel through the membrane without assistance?
Membrane permeability allows all substances to pass through easily.
Membrane permeability allows all substances to pass through easily.
What role do integral membrane proteins play?
What role do integral membrane proteins play?
The _____ model describes the structure of biological membranes as a mosaic of proteins and lipids.
The _____ model describes the structure of biological membranes as a mosaic of proteins and lipids.
How does increasing the temperature generally affect diffusion?
How does increasing the temperature generally affect diffusion?
Peripheral proteins are embedded within the lipid bilayer.
Peripheral proteins are embedded within the lipid bilayer.
What is facilitated diffusion?
What is facilitated diffusion?
The _____ gradient is established when there are different concentrations of a substance across the membrane.
The _____ gradient is established when there are different concentrations of a substance across the membrane.
What effect do unsaturated fatty acids have on membrane fluidity?
What effect do unsaturated fatty acids have on membrane fluidity?
What type of diffusion occurs through aquaporins?
What type of diffusion occurs through aquaporins?
Hypertonic solutions have a lower solute concentration than inside the cell.
Hypertonic solutions have a lower solute concentration than inside the cell.
What happens to a red blood cell when placed in a hypotonic solution?
What happens to a red blood cell when placed in a hypotonic solution?
Cells in __________ solutions will experience no net water movement.
Cells in __________ solutions will experience no net water movement.
Match the type of solution with its description:
Match the type of solution with its description:
Which solution would be best for rehydration after severe dehydration?
Which solution would be best for rehydration after severe dehydration?
Somatic cells divide by meiosis to produce identical daughter cells.
Somatic cells divide by meiosis to produce identical daughter cells.
Why is it important for intravenous (IV) fluids to be isotonic to blood?
Why is it important for intravenous (IV) fluids to be isotonic to blood?
What is the primary function of the centrosome in animal cells?
What is the primary function of the centrosome in animal cells?
Cilia are long bundles of microtubules used for cell movement.
Cilia are long bundles of microtubules used for cell movement.
What structure in the nucleus is responsible for making ribosomal subunits?
What structure in the nucleus is responsible for making ribosomal subunits?
The _____ is all of the DNA in an organism.
The _____ is all of the DNA in an organism.
Match the following organelles with their primary functions:
Match the following organelles with their primary functions:
What type of endoplasmic reticulum is involved in lipid synthesis?
What type of endoplasmic reticulum is involved in lipid synthesis?
Ribosomes are made of rRNA and proteins and are responsible for synthesizing lipids.
Ribosomes are made of rRNA and proteins and are responsible for synthesizing lipids.
What is the function of the Golgi complex?
What is the function of the Golgi complex?
Ribosomes translate mRNA into _____
Ribosomes translate mRNA into _____
What triggers the export of proteins from the rough endoplasmic reticulum?
What triggers the export of proteins from the rough endoplasmic reticulum?
Defective lysosomes can lead to disorders like Tay-Sachs disease.
Defective lysosomes can lead to disorders like Tay-Sachs disease.
What role do tRNAs play during translation?
What role do tRNAs play during translation?
The _____ membrane is continuous with the nuclear envelope.
The _____ membrane is continuous with the nuclear envelope.
What function is NOT associated with lysosomes?
What function is NOT associated with lysosomes?
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Study Notes
Cell Structure and Function
- Cells vary in shape and size, with approximately 200 different cell types in the human body.
- Cells are the basic unit of life, organizing functions through organelles, which behave as “little organs.”
- Eukaryotic cells have membranous organelles; prokaryotic cells do not.
Organelles in Eukaryotic Cells
- The plasma membrane is a flexible barrier that separates internal and external environments, regulating material exchange and facilitating intercellular communication.
- The cytoplasm includes all content between the plasma membrane and nucleus, providing an environment for chemical reactions.
Cytoskeleton
- Composed of microfilaments, intermediate filaments, and microtubules, aiding cell shape, stability, and movement.
- Microfilaments (actin and myosin) support structure and facilitate movement.
- Intermediate filaments provide tensile strength and anchor organelles.
- Microtubules (made from tubulin) segregate chromosomes during cell division and form motile structures like cilia and flagella.
Centroles and Cell Movement
- The centrosome organizes microtubules and contains centrioles, crucial for mitotic spindle formation.
- Cilia (short) and flagella (long) enable movement in various cells, including respiratory tract cells and sperm.
Nucleus
- Contains DNA within a double membrane structure called the nuclear envelope, perforated by nuclear pores.
- Houses the nucleolus, responsible for ribosomal subunit production.
DNA Organization
- DNA exists as chromatin (loose form) for transcription and can be tightly wound into chromosomes for cellular division.
- The genome encompasses all DNA in an organism.
Ribosomes and Protein Synthesis
- Ribosomes are composed of rRNA and proteins, critical for translating mRNA to proteins.
- The central dogma of biology describes DNA transcription to mRNA, followed by translation to protein.
- Ribosomes can bind multiple transcripts, allowing for the rapid production of many proteins.
Endoplasmic Reticulum (ER)
- The rough ER (rER) has ribosomes for protein synthesis, continuous with the nuclear membrane.
- The smooth ER (sER) synthesizes lipids, stores calcium, and detoxifies drugs.
Golgi Complex
- Modifies, sorts, and packages proteins received from the rER into vesicles for transport.
- Cisternae are membranous folds facilitating these processes.
Lysosomes and Peroxisomes
- Lysosomes are membrane-bound sacs containing digestive enzymes for breaking down cellular materials.
- Peroxisomes oxidize molecules, metabolizing fatty acids and detoxifying harmful substances.
Mitochondria
- Bounded by two membranes, crucial for ATP production through aerobic cellular respiration.
- Mitochondria are maternally inherited and have their own DNA, replicating independently.
Cell Division
- Somatic cells undergo mitosis and cytokinesis, with interphase stages G1, S (DNA replication), and G2 (organelle replication).
- Mitosis proceeds through prophase, metaphase, anaphase, and telophase, ultimately leading to cytokinesis.
Telomeres
- Telomeres protect chromosome ends from degradation; they shorten with age.
- Telomerase maintains telomere length in cancer cells, contributing to rapid cell division.
Meiosis
- Meiosis produces gametes (haploid cells) through two rounds of division: Meiosis I and II.
- Crossing over occurs in Meiosis I, allowing genetic variation.
Membrane Structure and Fluidity
- The plasma membrane is a fluid mosaic model with a phospholipid bilayer, cholesterol, and embedded proteins.
- Membrane fluidity allows for protein and lipid movement, essential for many cellular functions.
Transport Mechanisms
- Simple diffusion allows nonpolar molecules to move across membranes passively without energy input.
- Facilitated diffusion utilizes ion channels and carrier proteins to transport charged or polar substances down their concentration gradients.
- Active transport requires energy to move substances against their concentration gradient.
Membrane Permeability
- Membranes selectively permit certain molecules; gases like O2 and CO2 pass easily, while polar molecules require specialized channels.
Summary of Cell Functionality
- Cells maintain homeostasis through various organelles, structures, and processes, ensuring efficient interaction with their environment and division for growth and repair.### Active Transport
- Moves solutes against concentration gradients across membranes.
- Sodium-potassium (Na+-K+) pump maintains high Na+ concentration outside the cell and high K+ concentration inside the cell.
- Na+-K+ pump operates through ATP hydrolysis, changing its shape to transport ions.
Types of Active Transport
- Primary active transporters directly use ATP to move solutes against their gradients.
- Secondary active transporters utilize electrochemical gradients established by primary active transporters to move solutes.
- Simultaneous transport by secondary active transporters categorizes into:
- Symporters: both solutes move in the same direction.
- Antiporters: solutes move in opposite directions.
Inhibition of Active Transport
- Cyanide inhibits ATP synthesis in mitochondria, thus stopping all active transport processes.
Vesicular Transport
- Vesicles transport products between organelles.
- Endocytosis: movement into cells via vesicles.
- Exocytosis: movement out of cells, termed secretion in some instances.
- Both processes require ATP hydrolysis.
- Transcytosis involves endocytosis followed by exocytosis to move substances through cells.
Types of Endocytosis
- Receptor-mediated endocytosis: imports specific molecules.
- Phagocytosis: “eating” of substances or invaders by immune cells, leading to lysosomal digestion.
- Pinocytosis: “drinking” of dissolved solutes, also known as bulk-phase endocytosis.
Osmosis
- The movement of water from low solute concentration to high solute concentration across a semi-permeable membrane.
- Aquaporins facilitate the efficient movement of water across membranes.
Tonicity and Cell Behavior
- Solutions may vary in solute concentration affecting cell behavior:
- Hypertonic: higher solute concentration outside the cell, causing water to exit.
- Hypotonic: lower solute concentration outside the cell, leading to water entering the cell.
- Isotonic: equal solute concentration inside and outside the cell, resulting in no net water movement.
Clinical Application of Tonicity
- Intravenous (IV) fluids are typically isotonic to blood to maintain osmotic balance.
- Hypertonic solutions can lead to cell crenation, while hypotonic solutions can cause cell swelling.
Osmolarity
- Total concentration of solute particles in a solution, determining how a cell behaves in that solution.
Cell Division
- Somatic cells divide by mitosis, producing two identical daughter cells.
- Reproductive cells divide by meiosis, resulting in four nonidentical gametes.
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